Short wave radio transmitter



Feb, 18,1941. C, W, RICE 2,232,559

SHORT WAVE RADIO TRANSMITTER Original Filed Jan. 29, 1936 2 Sheets-Sheet l .Feb.`18, 1941. c. w. RxcE 2,232,559

SHORT WAVE RADIO TRANSMITTER original Filed Jan. 29, 193e 2 sheets-sheet 2 Inventor:

Chesterr W. Rte,

bg #Ma Hs Attorvneg.

` 4 where Patented `Feb.

Pari-:NT- OFFICE 2,232,559 e snoar wsvr. mimo TRANSMITTER chester w. nice. Schenectady, N. Y., assignmt@ General Electric Company, a corporation of New York vOriginal application January 29, 1936, Serial No. 61,377. Dividedand this-application June 25, 1938, Serial No.` 215,794

13 Claims.

My invention relates to short wave radio transmitters and more particularly to those of the electronic oscillator type in which the electron transit time governs the period of oscillation.

This application is a division of my copending application Serial No. 61,377, filed January 29, 1936, and assigned to the same assignee as the present application.

In order that my invention will be more readily understood, a brief discussion of the prior development in the art is necessary.` Barkhausen and Kurz discovered in 1919 that electronic oscillations are produced in a triode when a positive potential is applied to the grid and a small negative potential is applied to the plate. The explanation of these oscillations given by Barkhausen and Kurz is that electrons are accelerated from the cathode to the positive grid where some of the electrons, due to their high velocity, overshoot the grid and pass into the grid-plate region. In this region they are retarded and turned back in the direction of the grid. Those which pass the grid on their return trip and reach the neighborhood of the cathode are retarded and then once more accelerated in the direction of the grid.

Later, work by Zacek indicated that oscillations similar to those of Barkhausen and Kurz could be produced in circuits using a Hull mag- 3 netron of the concentric cylindrical diode type having a magnetic field in the direction of the electrode axis. In the magnetron, the electron orbits are determined by the combined effectof the electrostatic and the electromagnetic fleld,

Zacek found that the wave length for optimum oscillation strength was given approximately by const. H

).:wave length :magnetic field intensity an improved means for modulating oscillations. 1

A still further object of my invention is to provide an improved means for mounting and cooling electron discharge devices.

The novelfeatures which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however, both as to its organization and method of operation, together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawings in which Fig. 1 is an elevation partly in cross section of one embodiment of my invention. Fig. 2'is an enlarged cross sectional view of a portion ofthe transmitter which includes the modulating coil and the flux control ring. Fig. 3 is an enlarged cross-sectional view of the magnetron of Fig. 1. Fig. 4 is a crosssectional view of a tuning collar used in connection with the radiating member of Fig. 1. Fig. 5 is` an elevation partly in cross section of a modified form of my invention. e Fig. 6 illustrates in greater detail my improved method of cooling electron discharge devices. Fig. 'I is an elevation partly in cross-section of another embodiment of my invention wherein electro-magnets are used to produce the necessary axial magnetic fleld for magnetron operation.

Referring to Fig. 1 of the drawings, I have shown therein a transmitter embodying my invention, and which includes a permanent magnet l and an electron discharge device 2. Discharge device 2 is housed almost entirely within axial apertures 3 and 4 of two truncated conical pole pieces 5 and 6 which are securedto the ends of permanent magnet I. The discharge device is preferably of cylindrical form having a cylindrical metal anode 1, theopposite ends of which are supported in the respective apertures 3 and 4 of the pole pieces. 'I'he apertures themselves have an irregular contour las may be seen from the drawings. 'I'hese irregular contours provide suitable shoulders for mounting electron discharge device 2 as will hereinafter be pointed out.

It will be noted from the drawings that the right end of anode 1 is provided with a ring or collar 3 which closely fits against the inner surface of aperture 4 and which is held in position by the inner end of a split brass housing 9. Housing 9 is suitably form fitted within the aperture and is provided with a screw threaded follower 9 at the outer end which cooperates with corresponding threads in the pole piece whereby upon rotation of the follower 9 the inner end of the housing 9 is pressed rmly against the collar 9 which in turn engages a shoulder of aperture 4.

If water cooling be employed a suitable gasket II may be provided between the collar 6 and the shoulder I as presently will be described.

A second ring or collar I2 having a diameter less than the smallest diameter of the apertures 4 and 6 is provided on the opposite end of anode 1. Collar I2 is made with a smaller diameter than collar 8 in order that the electron discharge device may be readily inserted or removed from the pole pieces. The second advantage of providing the electron discharge device with a smaller collar at one end is that this permits unrestrained expansion and contraction of the electron discharge device within one of its mountings. It will be noted from the drawings that inner end of brass housing I3 slides over the top of collar I2. If water cooling be employed, a second gasket I4 is also provided at this end of the discharge device but in this case the gasket is placed around the collar rather than in front of it. As brass housing I3 is forced against gasket I4 by follower I3' the gasket expands in a radial direction and a fluid tight seal is formed thereby.

A non-magnetic spool I6 having a center aperture of the same diameter as that of aperture 3 and 4 snugly ilts the conical ends of pole pieces 6 and 6. Spool I6 has the dual function of providing a suitable mounting for a magnetic modulating coil and a flux control ring which will hereinafter be described and of providing a jacket about anode 1 which cooperates with pole pieces and 6 to form a water jacket for the electron discharge device. It will be readily seen from the drawings that apertures 3 and 4 together with the connecting spool I5 and the collars 9 and I2 form a confined space about the metal anode 1. By connecting inlet conduit conductor I9 which forms the central conductor of a concentric transmission line I9 the outer conductor of which comprises a hollow tube 20. An exposed portion 2l of conductor I9 constitutes the radiating member of the transmitting system.

'Ihis exposed portion 2I has a length determined in accordance with the radiation pattern desired. Conductor I9 is terminated for radio frequencies by a tuning disk 22 which slides on conductor I9, the electrical significance of which will hereinafter be more fully explained. Disk 22 is moved back and forth along conductor I9 until maximum output is obtained. Theoretically this places disk 22 at an odd multiple of a quarter wave length from the center of the cathode of discharge device 2. The antenna length may be held constant when tuning byfmeans of disk 22 by proper adjustment of a slide tube 23 which fits within the outer tube 23 and which may be coupled mechanically to disk 22 by suitable insulation. For this purpose disk 22 and tube 23 may be attached to non-conducting member 23. Thus by varying the position of member 23' tuning may be effected without varying the length of the antenna. Either of these members may, however, be adjustably connected to member 23' to permit varying the length of the antenna upon change of frequency.

A metal collar 24 (Fig. 4) is secured to the end of the slide tube 23 to render the radiation field pattern of the antenna more symmetrical. The outer ilange 25 of collar 24 has the same diameter as tuning disk 22 for symmetry. An inner constriction 25 is provided to reduce the radiation which would otherwise come out the end of the tube 23. Hence constriction 26 further improves the symmetry of the radiation pattern. A thin mica washer 26 which closely iits the antenna wire and is clamped between collar 24 and tube 23 serves to center and support the antenna wire.

A small circular plane reflector 21 is placed in front of exposed portion 2i to give the radiator unidirectional characteristics. 'I'he best results are obtained when reflector 21 is placed at approximately an odd multiple of a quarter wave length in front of exposed portion 2l for at that point maximum energy is reected in the desired direction. Radiator 2| is placed at approximately the optical focus of a large parabolic mirror 29 30 (such for example as a metal mirror of the type commonly employed for airport beacons having a 24" diameter and a lOl/2" focal length).

The metal frame 29 which carries reflector 21 is in the cathode circuit of the generator and serves to transmit the cathode current from conductor I9 back down the outer tube 20 of transmission line I9.

Two electrical energizing circuits are provided for the transmitter. A suitable low potential source 30 heats the cathode of discharge device 2 to the desired temperature. A variable resistor 3l is provided in series with source 30 to facilitate regulation of the potential applied across the cathode. The complete cathode heating circuit extends from the high side of source 30 through resistor 3l, conductor 32, the cathode of discharge device 2, conductor I9, jumper wire 33, frame 28, concentric conductor 20, binding post 34, conductor 36, to the grounded side of source 30.

A high potential (for example, 4000 volts) is applied to the anode of discharge device 2. The source of this potential is illustrated as a battery 36 but it is obvious that any other suitable source of supply may be used such as a rectifier or the like. Since modulation of the electronic oscillations may be obtained by causing a fluctuation of the anode potential at the modulating frequency, a modulator of this type is indicated conventionally by rectangle 31. The complete anode circuit extends from the high side source 36 through conductor 38, anode modulator 31, conductor 39, pole piece 6, the anode of discharge device 2, the cathode of discharge device 2, conductor I9, and thence through the cathode circuit previously traced to ground and to the negative side of source 36.

From the foregoing description, it is apparent that high frequency oscillations are produced solely on the cathode and in the associated cathode circuit. 'I'hat is, the cathode potential rises and falls above and below ground potential atv the circuit I employ may be termed a nlament swing circuit. To the best of my knowledge. prior art circuits have been confined to the see-saw type, that is, a circuit in which the potential of both the anode and the cathode vary at the oscillation frequency 'oras in a split anode magnetron in which the two anode halves vary with respect to each other at the oscillation frequency. The filamentswing type of circuit which I have devised permits the use of amassive anode, a feature which is necessary' if a large amount of power is to be dissipated. In the see-saw type circuit, theanode or anodes must high frequency waves is removed.

The frequency of oscillations generated in the magnetron of my invention is primarily a. function of the magnetic fleld intensity. Hence, it is desirable to provide a means for controlling the field intensity in order that the output frequency of the transmitter may be regulated. In the embodiment of my invention shown in Fig. 1, I have provided a variable magnetic shunt comprising two soft iron plates 40 and 4l, which slide on the under surfaces of pole pieces and 6 respectively, A control shaft 42 is provided with a set of right-hand screw threads and a set of left-hand screw threads, which threads cooperate with corresponding threads in plates 4i!V and 4l in such a manner that the plates may be moved closer together or farthervapart, depending upon the direction of rotation of the control shaft. Since the soft iron plates 40 and 4I act as a magnetic shunt path for the main field, a simple control of the magnetic field strength in the air gap between the pole pieces 5 and 6 is obtained. The whole equipment is mounted on a base 43.

It has been found that the power output of thev transmitter of my invention is extremely sensitive to the distribution of magnetic flux lines in the air gap. It will be observed that the pole pieces are shaped to concentrate the ux within the discharge device. That is, by reason of their receding faces, an efficient concentration of flux density is produced from pole to pole through the discharge device. While it will be understood that the pole pieces may have any suitable shape to effect this concentration of flux, the conical pole pieces described have been found to operate satisfactorily.

I have further found that the power output may be increased many fold, and sometimes as much as i3 times by placing a soft iron ring 44 near the air gap. Apparently, the soft iron ring 44 improves the distribution of flux in the air gap and for this reason I shall hereinafter designate ring 44 as a flux control ring.

Since the oscillation amplitude of the transmitter appears to be extremely sensitive to the distribution of ux lines.A in the air gap, modulation of the electronic oscillations may be obtained by superimposing a small magnetic field upon the main magnetic field, and by causing the small f leld to vary at modulating frequency. Such a small magnetic field may be obtained by mounting a small coil 45 in the air gap between pole pieces 5 and 6 and by applying thereto an alternating currentk having the frequency with which it is desired to modulate the short wave osciliations. A source of such alternating current is conventionally indicatedby a rectangle 46. The preferred location of flux control ring 44 and modulating coil 45 may be better seen by referring to Fig. 2 wherein I have shown an enlarged section of this portion of the transmitter.

,The electron discharge device 2 is illustrated in detail in Fig. 3 and includes an` axial cathode 41, a long concentric cylindrical anode 1, a pair of end envelopes 48 and 49 and a cathode tensioning spring 50. Cathode 41 is supported between two conductors I9 and 5I. Spring 5o is connected between conductor 5I and conductor 52 and maintains cathode 41 taut at all times. If spring 50 be not a satisfactory conductor of electricity, a jumper 53 may be employedv as a current carrying means between conductors 5l and 52. It is desirable to place the seal made between envelope 48 and conductor I9 at a voltage node on the conductor.

Anode 1 is built considerably longer than cathode 41 in order that substantially all of the electrons emitted from the cathode will eventually be collected on the anode 1. It should be noted that because the electron discharge device 2 is mounted with its opposite ends inl axial apertures of the pole pieces and that since a portion of the anode 1 is also located within these axial apertures, that the electrons in this region will pass rapidly to the anode for the reason that the magnetic field is greatly reduced within the apertures of the polev pieces. The combined effect of the long anode and the released magnetic field at the ends prevents electron puncture trouble at the ends of the discharge device.

Where a uniform straight magnetic iield, such as may be obtained by widely separating the pole pieces 5'and 6, is used for magnetron operation, it has been proposed to rotate the magnetron from 5 to l0 degrees with respect to the direction of the magnetic eld in order to increase the output.- I have found that this is not generally necessary where a slightly non-uniform magnetic field is provided. The special construction of pole pieces 5 and 5 having receding faces and provided with apertures for housing the ends of the electron discharge device produce the desired concentration of flux density in .the air gap and give it the desired slightly non-uniform character and in addition lprovide the desirable weak field within the axial apertures for electron release to the anode.

One of the important features of my invention is the method used for electrical tuning.- A metal disk 54 is mounted on conductor 5| to produce an approximate node of potential at that point of the conductor where the disk is located, thereby to reduce loss of energy from the corresponding end of the oscillator by reflecting this energy back into the active .part of the discharge device. The abrupt changey in impedance of conductor 5| caused by the presence of disk 54 produces the desired reflection. In practice, it has been found that tuning disk 54 causes greatest oscillation amplitude when located at a point slightly to discharge device will operate at one of the optimum output points which means that the frequency is determined by the position of disk 64 and other design factors. A frequency which will place disk 54 at approximately the orv E4 wave length point has given very satisfactory operation.

Disk 22 on conductor I9 functions as an electrical tuning element in the same manner as disk 54. Provision, however, is made for sliding disk 22 along conductor I9 until maximum output is obtained for any particular oscillation frequency generated in discharge device 2. Presumably, maximum output occurs when the disk, which produces an approximate potential node on the conductor, is located at an odd multiple of a quarter wave length from the center of cathode 41.

The operation of my transmitter is as follows: Cathod 41 is heated to the required temperature `by source 30 and anode 1 is raised to the proper high potential by source 36. The intensity of the magnetic field about discharge device 2 is then adjusted by the magnetic shunt 40-4l until a wave length is obtained at which the transmitter operates with good output. As previously indicated, optima o1' output occur at a number of different frequencies which are best found by trial. Tuning disk 22 has to be adjusted along conductor i9 until maximum power output is obtained.

As a result of the combined effect of the electrostatic and electromagnetic fields, electrons leave cathode 41 and follow spiral paths to anode 1. The transit time of an electron depends largely upon the strength of the magnetic field. Apparently, the electrons leaving cathode 41, migrate in groups at a frequency depending upon their transit time. In consequence thereof a high frequency wave is produced on conductor i9 and is radiated from the exposed portion 2|. Disk reflector 21 concentrates the radiated wave on the large parbolic reflector 29. Since exposed portion 2| is at the focus of the parabolic mirror 29, a highly directional radio wave is sent out from the system.

If a modulated wave be desired, either modulator 31 or modulator 46 may be placed into operation. Application of an alternating current having a frequency of the desired modulating signal to modulating coil 45 causes a variation of the flux distribution in the air gap between pole pieces 5 and 6 at the modulating frequency. This causes an amplitude modulation of the generated oscillations. Variation of the magnitude of the high voltage applied to anode 1 at the modulating frequency also causes an amplitude modulation of the electronic oscillations since a variation of anode potential also varies the output of the discharge device. If desired, both modulators may be used together.

Using a transmitter built in conformity to the above description, I have obtained exceptionally good results when operating at a wave length of only 4.8 centimeters. A regular broadcast program has been transmitted over a distance of many miles by using a carrier of this wave length and the signal was received well above the noise level. I have also been able to produce oscillations of even shorter wave lengths and also with suflicient power output for many practical applications.

A modified form of my invention is shown in Figs. 5 and 6. In this modification, a different method of cooling the magnetron is employed, a

slightly modified method of electrical tuning is adopted, and provision is made for rotating the electron discharge device from 5 to 10 degrees with respect to the magnetic field. Referring to Fig. 6, it will be seen that an electron discharge 5 device having an anode 1 is supported by a pair of metal jaws 60 and 6I. These metal jaws may be placed between the pole pieces and at right angles thereto to support the discharge device within the apertures of the pole pieces. Jaws 60 10 and 6| form a convenient method of support which readily permits an angular shift of the discharge device with respect to the magnetic field, that is, to a position out o-f parallelism with the axis of the magnetic field. These jaws also 15 provide an extremely simple method of conducting heat away from anode 1. An aperture 62 in jaw 60 and an aperture 63 in jaw 6| provide a passage for the cooling fluid received through inlet pipe 64 and discharged through outlet pipe 20 65. A short flexible U-shaped pipe 66 connects aperture 62 with aperture 63.

Referring now to Fig. 5, it will be seen that the cooling tubes 64 and 66 are shown herein arranged in a plane between the pole pieces and at 25 right angles thereto, which plane includes the jaws 60 and 6|.

This figure also shows a pair of tuning members 61 and 61', which are used in the place of the single tuning disk 54 previously described. 30 Tuning member 61 may be located at the same place that tuning disk 54 of Fig. 1 is located or it may be placed nearer the cathode 41 and within the metal anode 1. Tuning disk 61' is shown as being exterior to envelope 49. Tuning members 61 and 61' are so placed as to reflect energy back in the direction of the transmission line and thereby reduce back-end losses. Any stray energy which gets by tuning member 61 is substantially stopped by tuning member 61. A 40 shield 68 extends from tuning dis-k 61' back over a portion of anode 1 further to prevent loss of energy from this portion of the apparatus.

In order to permit rotation of the discharge device with respect to the magnetic field, a slightly different form of pole piece construction is necessary. Pole pieces 69 and 10 are provided with apertures 1i and 12 which preferably are of conical shape in the place of the form fitting apertures of pole pieces 5 and 6 of Fig. '1. These 50 conical apertures 1I and 12 permit an angular rotation of 5 to 10 degrees of the magnetron with respect to the magnetic field.

Where the magnetic field is substantially uniform over the active portion of the discharge device, the anode should extend beyond the effective electron emitting portion of the cathode at each end by at least the radius of the anode times the cotangent of the angle of tip, that is, the angle between the axis of the discharge device 'and that of the magnetic field. As previously pointed out, the provision of an anode which is substantially longer than the cathode entirely eliminates puncture trouble in the glass envelopes 48 and 49 at the ends of the magnetron by assuring that substantially all of the electrons are collected on the anode.

A further modification of my invention is shown in Fig. 7. In this modification the required magnetic iield about discharge device 2 is produced by a pair of large electromagnets 13 and 14. Two conical pole pieces 15 and 16 house discharge device 2 in a manner similar to pole pieces 5 and 6 of Fig. 1. Two sleeves 11 and 18 may be used to electrically insulate magnet coils 75 13` and i4 frompole piecesv 15 and '16. Inlet passage `l!! and outlet passage 80 for the :fluid control medium, are formed in the pole pieces in a somewhat different manner and connect with the space about the anode of the discharge device, as

may be seen from the figure. Suitable pipes 8i and 82 connect passages 19 and 80 tothe uid circulating system (not shown).

A return magnetic -path is provided by endl in Fig. 'l a form employing an electromagnet, I wish to point out that the permanent magnet has decided advantages with respect to the constancy Aof frequency which may be produced. Since the frequency of oscillation produced in my invention is dependent upon the intensity of the magnetic field, it is important that this field be held constant. It has been found `that this can best be accomplished by use of a permanent magnet, and further that by proper choice of materials a permanent magnet can be constructed for use in my invention which is not of objectionable dimensions. 'I'he magnet may comprise, for eX- arnple, 63% iron, 20% nickel, 12% aluminum, and 5% cobalt. I believe that I have been the first to provide a practical short wave oscillation generator of the magnetron type in which the advantage of permanent magnetism is taken to produce the main magnetic eld thereby to produce oscillations having frequency of improved constancy and extremely short wave length.

Herein, where I have used the term odd multiple of a quarter wave length, it will of course be understood that I include the multiple one.

While I have shown particular embodiments of my invention, it will of course be understood that I do not wish to be limited thereto since many modifications may be made both in the circuit arrangement and in the instrumentalities employed, and that I therefore contemplate by the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A short wave radio transmitter comprising a magnet, a pair of conical pole pieces secured to said magnet, an electron discharge device having an anode and a cathode, a substantial portion of said anode being housed within said conical pole pieces and the active portion of said cathode being located between said pole pieces, means including a water jacket between said anode and the walls of apertures formed in said pole pieces for cooling said discharge device, means including a variable magnetic shunt connected across said pair of pole pieces for adjusting the frequency of oscillations of said transmitter, means including a flux control ring adjacent the tips of said pole pieces for controlling the flux distribution between said pole pieces, a member for radiating the high frequency oscillations produced by said transmittor connected between the anode and the cathode of said oscillator through a concentric transmission line, electric tuning means including a tuning member located on said radiating member at an odd multiple of a quarter of the wave length of said oscillations from the center of said cathode, and means for modulating said high frequency oscillations, by varying the flux distribution in the air gap between said pole pieces.

2. In a short wave radio transmitter, the combination including a magnet, a pair of pole pieces, an oscillator having an anodeand a cathode, a substantial portion of said anode'being housed within said pole pieces and the active portion of said cathode being located between said pole pieces, and means for modulating the high frequency oscillations produced byv said oscillator by varying the flux .distribution in the Vair gap between said pole pieces at the desired vmodulating frequency, said means being constituted by a winding located between said `pole pieces and surrounding said active portion of said cathode, a source of said modulating frequency, and means to impress said modulating frequency on said winding from said source.

3. In a short wave radio transmitter, the combination including a permanent magnet, a pair of conical pole pieces secured to the ends of said permanent magnet, an electronic oscillator hav-` ing an anode and a cathode, a substantial 'portion of said anode being housed within saidy conical pole pieces and the active portion of said cathode being located between said pole pieces, and magnetic means for producing am-v plitude modulation in said oscillator by varying the flux distribution in the air gap between said pole pieces at the desired modulating frequency, said means being constituted by a winding located between said pole pieces and surrounding said active portion of said cathode, a source of said modulating frequency, and means toi impress said modulating frequency on said winding from said source.

4. The method of modulating high frequency oscillations produced in a magnetron, said magnetron comprising a magnet having a pair 0f conical pole pieces and an electron discharge device having a short linear cathode and a relatively long cylindrical anode enclosing said cathode, a substantial portion of said anode being housed within said pole pieces and the active portion of said cathode being located between said pole pieces, said magnet subjecting said electron discharge device to a magnetic field, which includes generating oscillations of a desired modulating frequency, utilizing said last named oscillations to generate a magnetic field varying at the modulating frequency, and utilizing said varying magnetic eld to vary the distribution of magnetic flux lines within said electron discharge devices at the modulating frequency.

5. The method of modulating the high frequency oscillations produced by a magnetron, said magnetron comprising a magnet having a` pair of conical pole pieces and an electron discharge device having a short linear cathode and a relatively long cylindrical anode enclosing said cathode, a substantial portion of said anode being housed within said pole pieces and the active portion of said cathode being located between said pole pieces, said magnet subjecting said electron discharge device to a strong magnetic field, which includes generating oscillations of a desired modulating frequency, utilizing said last named oscillations to generate a small magnetic eld varying at the modulating frequency, and superimposing said small magnetic field upon the strong magnetic field.

6, In an electronic, oscillator, the combination comprising a cathode, a plurality of conductors connected to saidcathode, an anode, meansy tuning member-being located exterior to the envelope of said oscillator on one of said conductors and all of said tuning member being placed at approximately an odd multiple of a quarter of said wave length from the center of said cathode.

7. In4 combination, an electron discharge device comprising an anode and a cathode extending axially thereof, means to energize said anode and cathode and means to produce a strong magnetic field within said discharge device and extending longitudinally thereof, means comprising said last-named means to produce high frequency oscillations on said cathode, radiating means for said oscillations connected to one end of said cathode, and means substantially to confine the transmission of oscillation from said cathode to said radiating member.

8. In combination with an oscillator having a cathode on which high frequency oscillations are produced, a pair of conductors connected to said cathode, an anode, and a plurality of tuning members, said tuning members being located on said conductors and arranged to confine said high frequency oscillations to'the portion of said conductors between said tuning members.

9. In combination with an electronic oscillator having a linear cathode and an anode concentric therewith, conductors extending from opposite ends of said cathode, a tuning member in the envelope of said oscillator on one of said condrctors and at a distance from the center of said cathode equal approximately to an odd multiple of a quarter wave length of the wave on which said oscillator operates, and a second tuning member exterior to the envelope of said oscillator adjustably mounted on the same conductor as said first tuning member at a distance from the center of said cathode equal to an odd multiple of said quarter Wave length.

10. In combination with an electronic oscillator having a linear cathode and a cylindrical anode concentric therewith, conductors extending from opposite ends of said cathode, a tuning member located on one of said conductors at a distance from said cathode equal approximately to an odd multiple of a quarter wave length of the wave on which said oscillator operates, a second tuning member mounted on the same conductor as said first tuning member at a distance from said cathode equal approximately to a different odd multiple of said quarter wave length of said wave, and a cylindrical shield extending from said second tuning member over a portion of said anode, thereby to reduce transmission of high frequency energy from said cathode along said one conductor.

11. In a short wave radio transmitter, the combination including an oscillator having a cathode and an anode, a radiating member connected to said oscillator and a. tuning member located on said radiating member at such a point of the wave on which said transmitter operates as to produce an approximate voltage node at said point.

12. In a short wave oscillator, the combination comprising an electron discharge device having an anode and a cathode, means for causing the potential of the cathode to vary at the frequency of the desired signal wave, a radiating member connected to said cathode,an electrical tuning member, means to locate all of said tuning member on said radiating member at approximately an odd multiple of a quarter of a wave length of the oscillation of said frequency from the center of said cathode, and means for maintaining fixed the potential of said anode.

13. The combination comprising an oscillator having two electrodes, means for varying the potential of one of said electrodes at the desired oscillation frequency, radiating means for the oscillations of said frequency, a conductor to connect said radiating means to one of said electrodes, an electrical tuning member located on said conductor, an electrical tuning member located on said radiating means, each of said tuning members being placed at approximately an odd multiple of a quarter of the wave length of the oscillations of said frequency from the center of said one of said electrodes, and means for maintaining the remaining electrode at a substantially constant potential.

CHESTER W. RICE. 

